UV-C LED sources design and characterization (original) (raw)
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We present the electrical and optical design, assembling, and thorough experimental characterization of two compact arrays of short-wavelength ultraviolet (UV-C) light-emitting diodes (LEDs) suitable for near-field irradiation. Through a combination of technical expedients, we have achieved effective thermal management such that long-lasting irradiations are possible without appreciable deterioration of UV-C emission. We successfully used these compact UV-C LED arrays for long lasting irradiation tests aimed at generating the biosynthesis of defensive metabolites that enhance the resistance of plants and fruits to pathogen attacks. Finally, we comment on the possibility of implementing these compact UV-C sources on robotic systems to make an automated device suitable to reduce pesticide use in agricultural crops.
UV LED Technology : The Times They are A-Changin ’
2018
Introduction UV photonics, photoreaction and photoreactor systems are the key elements of many industries. Recent advances in a new UV source, the ultraviolet light emitting diode (UV LED), create the opportunity for the development of novel UV-based technologies and devices. In fact, UV LEDs could potentially transform the UV-based industry by not only advancing the design and application of current UV modules, but also enabling the creation of entirely new products and markets.
Junction temperature control of UV-C LEDs based on a thermoelectric cooler device
Microelectronics Reliability, 2019
Junction temperature (T J) control is mandatory to improve the optical efficiency, lifetime and the wavelength accuracy of the UV-C LED light sources. Thermoelectric cooler devices allow a critical control of the junction temperature, based on direct measurement of the solder point temperature. A PID control technique was implemented to control the voltage in the TEC devices and therefore the desired range of junction temperatures. The PID parameters are obtained with computational simulations based on physical models and experimental recordings of the solder temperature dynamics. Optical performance improves is demonstrated and the better lifetime could be achieved.
Degradation effects of the active region in UV-C light-emitting diodes
Journal of Applied Physics, 2018
An extensive analysis of the degradation characteristics of AlGaN-based ultraviolet light-emitting diodes emitting around 265 nm is presented. The optical power of LEDs stressed at a constant dc current of 100 mA (current density = 67 A/cm2 and heatsink temperature = 20 °C) decreased to about 58% of its initial value after 250 h of operation. The origin of this degradation effect has been studied using capacitance-voltage and photocurrent spectroscopy measurements conducted before and after aging. The overall device capacitance decreased, which indicates a reduction of the net charges within the space-charge region of the pn-junction during operation. In parallel, the photocurrent at excitation energies between 3.8 eV and 4.5 eV and the photocurrent induced by band-to-band absorption in the quantum barriers at 5.25 eV increased during operation. The latter effect can be explained by a reduction of the donor concentration in the active region of the device. This effect could be attri...
The increasing resistance of methicillin-resistant Staphylococcusaureus to antibiotics is a major challenge faced by mankind in the history of medical science and according to United Nations, 700-000 patients worldwide die every year from an infection with multidrug-resistant organisms (MROs). Aluminum gallium nitride-based 228 nm Far-ultraviolet-C (Far-UVC) light sources can be safely used as a germicidal application in both manned as well as in unmanned environments against these MROs. Previously, the 228 nm Far-UVC light-emitting diode (LED)with emission power of 1 mW was reported by our group, however, the value of external quantum efficiency (EQE) was not reported using conventional thick Ni(20 nm)/Au (100 nm) p-electrode. Herein, an improved Far-UVC LED on c-Sapphire is attempted using a special technique in SR4000 type of metal-organic chemical vapor deposition reactor to control the Al composition in n-AlGaN buffer and across the 2 inch-wafer. As a result, the light emission power of 1.8 mW and EQE of0.32% in 228 nm Far-UVC LED are successfully achieved using very thin p-electrode(Ni/Au). However, a relatively high junction temperature of ≈100°C around the-junction of Far-UVC LED is observed. Finally, some simple heat-sink modules for heat dissipation of Far-UVC LED panel with light power of 30 mW are implemented.
UV Light Emitting Diodes; Their Applications and Benefits
… , Los Angeles, CA, 2007
The field of ultraviolet (UV) processing and analytics is becoming more and more widespread. The light sources for these applications remain based on the old technology of mercury lamps, while, for some applications, there could be many advantages of having a low voltage, small light source with tunable emission wavelengths. We report on ultraviolet light emitting diodes (UV-LEDs). LEDs are becoming commonplace in the visible light applications, but there remain many technical barriers when transferring this technology into the shorter UV light ranges. Recent advances have produced UV-LEDs fabricated on bulk native AlN substrates yielding devices emitting in the 280 nm to 340 nm range. Devices are fabricated using standard semiconductor processing techniques in various geometries to accommodate specific imaging applications. These UV-LEDs are compact, rugged and efficient, enabling new applications in existing markets as well as opening new market areas.
UV LEDs for high-current operation
Journal of Physics: Conference Series, 2013
In this paper we report on results of development of ultraviolet light-emitting diodes (UV LEDs) based on GaN/AlGaN heterostructures grown on Al 2 O 3 (0001) substrates by chloride-hydride vapour phase epitaxy (CHVPE). Both UV LED heterostructures and packaged dies are investigated. UV LEDs proved performance capability at current density up to 125 A/cm 2 and revealed wall-plug efficiency (WPE) of 1.5% at operating current of 20 mA.
Investigation of the temperature dependent efficiency droop in UV LEDs
Semiconductor Science and Technology, 2013
The influence of the dislocation density and the carrier-confining potentials on the temperature dependent behavior of the external quantum efficiency (EQE) of near-ultraviolet light-emitting diodes (LEDs) at different current densities has been investigated. The LED efficiencies were found to be very temperature sensitive with characteristic temperatures ranging from 48 to 207 K. In the low current density region the temperature dependence of the EQE is mainly dominated by the Shockley-Read-Hall recombination and hence the dislocation density of the device. In the high current density region, carrier leakage from the quantum wells is the main factor influencing the decrease in the EQE with ambient temperature, and in this region the LEDs become less temperature sensitive with increasing quantum well barrier height.
Designing light-emitting diode arrays for uniform near-field irradiance
Applied Optics, 2006
We analyze the first-order design of light sources consisting of multiple light-emitting diodes (LEDs) to uniformly illuminate a near target plane by considering each single LED as an imperfect Lambertian emitter. Simple approximate equations and formulas are derived for the optimum LED-to-LED spacing, i.e., the optimum packaging density, of several array configurations to achieve uniform near-field irradiance.
Investigate the Double Peaks in Main Emission of UVB LEDs
2021
In this study we suppressed the parasitic emission caused by electron overflow found in typical UVB light-emitting diodes (LEDs). Furthermore, modulation of the p-layer structure and doping profile allowed us to decrease the relaxation time of the holes to reach conditions of quasi-charge neutrality in the UVB quantum well. Our UVB LED (sample A) exhibited a clear exciton emission, with its peak near 306 nm and a band-to-band emission at 303 nm. The relative intensity of the exciton emission of sample A decreased as a result of a thermal energy effect. At temperatures of up to 363 K, sample A displayed the exciton emission. Our corresponding UVC LED (sample B) exhibited only a Gaussian peak emission at a wavelength of approximately 272 nm.